Field of the Invention
The present invention relates to an imaging apparatus and more particularly a technique of handling a RAW image of a still image or a moving image.
Description of the Related Art
In an imaging apparatus, raw image information (RAW image) captured by an image sensor undergoes a debayer process (demosaicing process) and is converted into signals formed of luminance and color differences, and a so-called developing process such as noise removal, optical distortion correction, optimization of an image, and the like is performed on each signal. Then, the imaging apparatus compression-encodes the luminance and color difference signals that have been developed and records the resultant signal in a storage medium.
On the other hand, there exists an imaging apparatus that can record a RAW image. The RAW image of such an apparatus is advantageous in that correction and degradation of an original image obtained immediately after an imaging operation by the image sensor are suppressed to a minimum and that editing is possible after shooting. Hence, advanced users favor using the RAW image. However, since the RAW image contains an enormous amount of data, it is desirable to suppress the data amount so that as many images as possible are recorded in a storage medium which has limited space. Hence, the data amount is suppressed by compressing the RAW image. However, depending on the shooting condition, image quality degradation may occur due to compression.
Japanese Patent Laid-Open No. 2000-152240 discloses an arrangement in which quantization is changed in accordance with the characteristics of the human visual system in order to suppress image quality degradation. However, in the technique disclosed in Japanese Patent Laid-Open No. 2000-152240, if a RAW image whose data changes depending on the shooting condition is used, performing the developing process will change the luminance, the contrast, and the like that were recorded in the image data at the time of encoding. Therefore, using the image data at the time of encoding, which was recorded before the developing process, can cause image quality degradation even if optimal quantization is performed in accordance with the characteristics of the human visual system.